In the field of printing, the most common type printer has been the printer which impacts against record media that is caused to be moved past a printing line or line of printing. As is well-known, the impact printing operation depends upon the movement of impact members, such as print hammers or wires or the like, which are typically moved by means of an electromechanical system and which system enables precise control of the impact members.
In the field of dot matrix printers, it has been quite common to provide a print head which has included therein a plurality of print wire actuators or solenoids arranged or grouped in a manner to drive the respective print wires a precise distance from a rest or non-printing position to an impact or printing position. The print wires are generally either secured to or engaged by the solenoid plunger or armature which is caused to be moved such precise distance when the solenoid coil is energized and wherein the plunger normally operates against the action of a return spring.
It has also been quite common to provide an arrangement or grouping of such solenoids in a circular configuration to take advantage of reduced space available in the manner of locating the print wires in that area from the solenoid to the front tip of the print head adjacent the record media. In this respect, the actuating ends of the print wires are spaced in accordance with the circular arrangement and the operating or working ends of the print wires are closely spaced in vertically-aligned manner adjacent the record media. The availability of narrow or compact actuators permits a narrower print head to be used and thereby reduces the width of the printer because of the reduced clearance at the ends of the print line. The print head can also be made shorter because the narrow actuators can be placed in side-by-side manner closer to the record media for a given amount of wire curvature.
In the wire matrix printer, the print head structure may be a multiple-element type with the wire elements aligned in a vertical line and supported on a print head carriage which is caused to be moved or driven in a horizontal direction for printing in line manner, while the drive elements or transducers may be positioned in a circular configuration with the respective wires leading to the front tip of the print head.
Alternatively, the printer structure may include a plurality of equally-spaced, horizontally-aligned single-element print heads which are caused to be moved in back-and-forth manner to print successive lines of dots in making up the lines of characters. In this latter arrangement, the drive elements or transducers are individually supported along a line of printing. These single wire actuators or solenoids are generally tubular or cylindrically shaped and include a shell which encloses a coil, an armature and a resilient member arranged in manner and form wherein the actuator is operable to cause the print wire to be axially moved a small precise distance in dot matrix printing.
In the concept of dot matrix printing, it is generally desired to place the print element actuators in a position to allow characters to be printed in serial manner and this placement requires that the print wire or like print element actuators be very closely spaced with respect to each other. Since the print actuators are generally much larger in size then the diameter of the printed dot, a relatively long wire or like element must be provided to bring the desired print activity from its source, such as moving armature or plunger or the like, to a vertical closely-spaced column arranged in a pattern such that the column of closely-spaced, tangentially coincident or overlapping dots will be produced on the record media if all actuators are fired or actuated at one time.
Representative documentation in the field of wire matrix print heads includes U.S. Pat. No. 3,675,172, issued to N. J. Petusky on July 4, 1972, which discloses a damping system having an energy transfer element between two restraining walls, one of which is of energy absorptive material, the transfer element being engageable by an actuator element.
U.S. Pat. No. 3,787,791, issued to J. H. Borger et al. on Jan. 22, 1974, discloses a solenoid having a plunger engageable with a flat spring which fits in recesses of a plastic spring seat.
U.S. Pat. No. 3,929,214, issued to D. G. Hebert on Dec. 30, 1975, discloses a print head having a unitary connector with an O-ring inserted in a groove and acting as a shock absorber to provide a reference surface for the stylus striking ends of the armature.
U.S. Pat. No. 3,994,381, issued to D. G. Hebert on Nov. 30, 1976, discloses a print head having an armature retainer loaded by a spring and including a backstop or bumper cushion which cushions the return shock of the armature.
U.S. Pat. No. 4,051,941, issued to D. G. Hebert on Oct. 4, 1977, discloses a print head having an armature retainer with a shock absorbing O-ring member engageable by ends of the armatures. The retainer includes a central disk portion secured with a screw.
U.S. Pat. No. 4,081,067, issued to R. L. Schrag et al. on Mar. 28, 1978, discloses a print head having a centrally disposed dampening member and a unitary connector with a groove carrying an O-ring to act as a shock absorber for the armatures. A screw and a washer secure the unitary connector to the frame.
U.S. Pat. No. 4,140,406, issued to P. H. Wolf et al. on Feb. 20, 1979, discloses a print head having an armature retainer secured by a screw and carrying adjusting elements engageable with a rubber damper against ends of the armatures.
U.S. Pat. No. 4,200,401, issued to K. L. Roy et al. on Apr. 29, 1980, discloses a solenoid having an impact disk against a block or pad of energy absorbing rubber or like material to take the impact of the print wire.
U.S. Pat. No. 4,209,260, issued to F. Jung on June 24, 1980, discloses a print head having a back plate and a central member with adjustable means for the armatures.
U.S. Pat. No. 4,230,412, issued to D. G. Hebert on Oct. 28, 1980, discloses a cover plate having an elongated adjustment and abutment hub member secured by a screw, and an O-ring member against one end of the hub member and engageable by ends of the armatures.
U.S. Pat. No. 4,272,748, issued to P. E. Fugate et al. on June 9, 1981, discloses a solenoid having a rebound and energy absorbing arrangement which employs a block of energy-absorbing dead elastomeric material held in a partially compressed state by an impact plate.
U.S. Pat. No. 4,320,981, issued to M. Harrison et al. on Mar. 23, 1982, discloses a print head having a backplate with adjusting screws and shock absorbing material between the armatures and the backplate.
U.S. Pat. No. 4,382,701, issued to K. B. Davenport on May 10, 1983, discloses an armature support frame carrying resilient plugs forming backup dampers with adjustment screws.
U.S. Pat. No. 4,401,392, issued to J. E. Blomquist et al. on Aug. 30, 1983, discloses a print head having an armature retaining screw and a resilient backstop against which the ends of the armatures engage.
U.S. Pat. No. 4,407,591, issued to C. Adamoli et al. on Oct. 4, 1983, discloses a ballistic wire matrix print head having a single rear plastic support connected by means of a capping nut, along with a first ring of resilient material on the support to keep the armatures biased against pole surfaces, and a second ring of resilient material on the support engaging with inner ends of the armatures.
And, U.S. Pat. No. 4,478,528, issued to D. G. Hebert on Oct. 23, 1984, discloses an armature retaining cover plate with resilient cushion means and/or biasing spring means to dampen the return movement of the armature members.